Cognitive therapy has been shown to be at least as effective as, if not more effective than, pharmacotherapy in the treatment of non-bipolar outpatient depressives and, perhaps, more effective in terms of preventing subsequent relapse. To date, no studies have examined the efficacy of combining cognitive therapy with pharmacotherapy. Similarly, no studies have attempted to extend cognitive therapy into a variety of subtypes of depressions, e.g. bipolar, inpatient (and/or psychotic) depressions. Further, no adequately controlled study has yet compared the relative efficacy of group cognitive therapy with individual cognitive therapy, either with or without medications. This project consists of a coordinated series of studies examining the comparative efficacies of cognitive therapy, pharmacotherapy, and combined cognitive-pharmacotherapy in the treatment of depression. Five specific studies are proposed including three with outpatient samples (2 non-bipolar, 1 bipolar), and two with inpatients (1 non-bipolar, 1 bipolar). Treatment efficacy will be evaluated in terms of response to treatment, prevention of relapse, and minimization of dropout rates. The use of a common core battery and a common treatment protocol will facilitate comparisons across populations and settings. Finally, a series of cross-lagged panel analyses and multivariate analyses will be utilized to explore: 1) a variety of hypotheses regarding the mechanisms of change associated with each treatment modality (e.g., the relationships between biochemical indicies, cognitive processes, and levels of syndrome depression), and 2) potential predictors of both response to treatment and maintenance of treatment gains.